Rotary impact tool



Dec. 3, 1968 R. c. FALTER 3,414,065

ROTARY IMPACT TOOL Filed April 26, 1967 2 Sheets-Sheet 1 FIG-l 43 VENTOR IN RONALD c. FALTER ATTORNEYS Dec. 3, 1968 c, FALTER 3,414,065

ROTARY IMPACT TOOL- Filed April 26, 1967 2 Sheets-Sheet 2 x ya X 38 6'5 34 5 United States Patent 3,414,065 ROTARY IMPACT TOOL Ronald C. Falter, Dayton, Ohio, assignor to Rockwell Manufacturing Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Apr. 26, 1967, Ser. No. 633,761 6 Claims. (Cl. 173-935) ABSTRACT OF THE DISCLOSURE A rotary motor drives a cup-shaped hammer with inwardly projecting lugs. An anvil extends into the hammer and supports a pair of dogs connected by a yoke mounted on a sleeve which can slide on a splined spindle rotating with the anvil. A spring urges the sleeve to move the dogs out of the path of the lugs. A cam mounted on the hammer engages a ball carried by the sleeve and pushes against the spring causing the hammer to impact the anvil through the dogs in response to rotation of the hammer relative to the anvil.

Background of the invention The field of this invention involves a rotary impacting tool which is driven by a rotary motor, particularly a portable hand-held tool. The motor rotates a hammer which, in turn, drives an anvil having a drive shank for attaching to a tool element such as a socket wrench. In some early constructions, axially moving components are carried by the hammer, or the hammer itself moves, and are urged to a spring into normal engagement with the anvil. A typical construction of this type is shown in US. Patent No. 3,195,702. More recently, tools of this type embody a hammer and anvil which are normally disengaged. An overload clutch connects the hammer to the anvil and is selected and constructed so that when the torque resistance on the anvil reaches a predetermined value, the clutch will disengage and cause the hammer to gain momentum after which the hammer automatically strikes the anvil and thereby produces successive impacts on the anvil.

It is desirable to minimize the mass of the axially movable or reciprocating components of the clutch to minimize the recoil action on the hand of the operator supporting the tool. Furthermore, it is desirable to construct the clutch so that neither the hammer, the anvil nor the reciprocating components are subject to primarily a shearing force during impacting, but are subjected more to compression or crushing forces to avoid breaking any of the components. Of course, it is also desirable to minimize the cost of the clutch components which are subjected to greatest wear so that these components can be economically and conveniently replaced.

One prior art rotary impacting tool provides the above mentioned features by incorporating a generally cylindrical hammer having a pair of diametrically opposed axially extending internal slots which receive pin-like dogs. An axially moving yoke member connects the dogs and is actuated by a cam to move the dogs axially along the hammer into engagement with ears or lugs projecting outwardly from the anvil, such that the hammer impacts the anvil through the dogs.

The hammer structure required for this construction is rather difficult and expensive to construct and assemble, and does not have substantial mass at a maximum distance from the axis of rotation to obtain the maximum moment of inertia in a tool of overall minimum diameter. In addition, the outwardly projecting ears or lugs on the anvil do not achieve maximum torsional rigidity to minimize rotational spring back of the tool during impact.

Patented Dec. 3, 1968 Summary of the invention The present invention is directed to a rotary impacting tool which incorporates a hammer, anvil and clutch mechanism of improved construction such that the hammer and anvil can be economically constructed and assembled, while obtaining a maximum moment of inertia in the hammer as well as maximum torsional rigidity in the anvil, in addition to minimizing the mass of the reciprocating components of the clutch and the shearing forces between the hammer and anvil during impacting.

In general, the above features are provided by an impact tool wherein a cup-shaped hammer has a cylindrical outer surface and includes diametrically opposed inwardly projecting lugs adjacent its open end. A generally cylindrical anvil projects into the hammer and has a pair of axially extending grooves formed on its outer cylindrical surface for slidably supporting pin-like 'dogs.

The clutch arrangement includes an axially extending spindle rigidly connected to the anvil and provided with a spline which supports a sleeve connected to the dogs by a yoke, thus there is no relative rotation between the dogs and the anvil. A cam carried by the hammer engages a ball carried by the sleeve, and a spring biases the sleeve, ball and cam together so that when the anvil stops due to torsional resistance, continued rotation of the hammer produces axial movement of the sleeve against the force of the spring, thereby moving the dogs into the path of the inwardly projecting lugs of the hammer, whereby the hammer produces an impact on the anvil through the dogs.

More specific features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

Brief description of the drawings FIG. 1 is an enlarged axial section of the forward end portion of a rotary impact tool constructed in accordance with the invention;

FIG. 2 is an exploded perspective view of the internal components shown assembled in FIG. 1;

FIG. 3 is a section taken generally on the line 3-3 of FIG. 1;

FIG. 4 is a section taken generally on the line 4-4 of FIG. 1;

FIG. 5 is a section taken generally on the line 5-5 of FIG. 7 at the moment of impact;

FIG. 6 is a section taken generally on the line 6-6 of FIG. 1 after impact; and

FIG. 7 is a fragmentary axial section taken at the moment of impact.

Description of the preferred embodiment Referring to FIG. 1, an impact tool incorporating the features of the invention includes a cylindrical housing 10 having a forward end portion 11 of reduced diameter and connected to the forward end portion of a housing 12 which encloses a reversible rotary motor, such as sliding vane-type pneumatic motor 15. The motor has a forwardly extending rotor shaft 16 rotatably supported by an antifriction bearing 17 retained within a forward end plate 18 of the motor. Since the detailed construction of the motor is well known in the art it has not been included herein.

An external spline 20 and an axially extending bore 21 are formed on the forward end portion of the rotor shaft 16. A cup-shaped hammer 25 having a cylindrical external surface 26, includes an end wall 27 having a central bore 28 with an internal spline for mounting the hammer 25 on the rotor shaft 16. The hammer 25 is bored to form a cylindrical surface 30 concentric with the bore 28 and an intermediate flat radial surface 31. The diameter of the surface 30 is approximately one-half of the outside diameter of the cylindrical surface 26 so that the hammer has substantial mass surrounding and outwardly of the rotor shaft 16. The hammer 25 is also bored to form a larger cylindrical surface 34 from which a pair of diametrically opposed lugs (FIGS. 1 and 4) project inwardly. As shown in FIG. 4, the cylindrical surface 34 extends between the lugs 35 and curves into each lug by a large radius surface 36 to form a pair of arcuate shaped cavities 38.

A counterbore 40 (FIG. 1) is formed within the forward end portion of the hammer 25 and receives the outer race of an antifriction bearing 42. A cylidnrical liner 43 is secured to the forward end portion 11 of the housing 10 and supports a sleeve-type bearing 45 having an inner flange 46 provided with an annular notch 47 which receives a portion of the inner race of the bearing 42.

An anvil 50 includes a cylindrical portion 51 which is rotatably supported by the bearing 45 and a driving end portion 52 having a square cross-section (FIG. 2). A flat forward face 54 is formed on the anvil 50 and abuts the flange 46 of the bearing 45, and a cylindrical surface 55 extends from the face 54 and forms a seat for the inner race of the bearing 42. A circumferential groove 57 is formed within the cylindrical surface 55 and receives an O-ring 58 for damping vibration of the bearing 42.

A cylindrical surface 60 (FIGS. 2 and 3) slightly smaller in diameter than the surface 55 is formed on the anvil 50 and is interrupted by a pair of diametrically opposed semi-cylindrical grooves 62 which extend into the surface 55. A pin-like dog 65 is mounted within each of the grooves 62 and includes a cylindrical portion 66 connected by a tapered portion 67 to a cylindrical neck portion 68 and a flange portion 69.

The rear end portion of the anvil 50 is formed with a cylindrical bore 72 having a fiat end surface 73 from which extends an axially extending hole 74. A spindle 75 includes a cylindrical head 76 which is press-fitted into the bore 72 to abut the surface 73. A notch 77 is for-med within the head 76 and receives the projecting end portion of a pin 78 press-fitted into the hole 74 to prevent relative rotation of the spindle 75 relative to the anvil 50. A cylindrical stud 80 is formed on the opposite end portion of the spindle 75 and is rotatably received within the bore 21 formed within the forward end portion of the rotor shaft 16.

An external spline 82 is formed on the spindle 75 and receives a corresponding internal spline 83 formed within a tubular sleeve 85 slidably mounted on the spindle 75. The forward end portion of the sleeve 85 includes an internal counterbore 86 and an annular external seat 88. A yoke plate 90- is mounted on the seat 88 and is retained by a snap ring 91.

The rear end portion of the anvil 50 has a cylindrical bore 94 which is slightly larger in diameter than the outside diameter of the sleeve 85 and is interrupted by a pair of radially extending slots 95 for receiving diametrically opposed and outwardly projecting tabs 97 (FIG. 3) formed on the yoke plate 90. Each tab 97 includes a U-shaped portion 98 which is spaced between the tapered portion 67 and flange portion 69 and partly surrounds the neck portion 68 of the corresponding dog 65.

Referring to FIG. 5, the sleeve 85 is provided with an arcuate slot 99 which extends approximately 90 around the periphery of the sleeve. A ball 100 is retained within the slot 99 and is confined therein by the internal cylindrical surface 30 for-med within the hammer 25. An annular cam is retained within the hammer 25 against the flat annular surface 31 and includes a flat ca-m surface 106. The cam 105 includes an arcuate portion forming generally an axially extending symmetrical V-shaped cam surface 108 which extends from the surface 106 and has a peak 110. An axially extending pin 112 interconnects the cam 105 with the hammer 25 to prevent relative rotation.

A compression spring 115 is mounted on the spindle 75 and includes a forward end portion engaging the spindle head 76 and a rearward end portion which is received within the counterbore 86 of the sleeve 85. The spring 115 is thus effective to bias or urge the sleeve 85 and ball 100 rearwardly into normal engagement with the flat surface 106 of the cam 105 (FIG. 1) thereby holding the dogs 65 rearwardly within the corresponding groove 62.

When the impact tool is in use, as for example, in tightening a machine screw and the torque on the anvil 50 reaches a predetermined value, the rotation of the anvil 50 stops. Continued rotation of the hammer 25 by the motor 15, however, forces the ball 100 up one side of the V-shaped cam surface 108 thereby causing the sleeve 85 to move forwardly to compress the spring 115 and to move the dogs 65 into the corresponding cavities 38 and the rotational path of the lugs 35.

Approximately 10 of rotation before the lugs 35 engage the corresponding dogs 65, the ball 100 rolls over the peak 110 of the cam 105. The forward inertia of the dog 65 and the sleeve 85, however, holds the dogs within the path of the lugs 35 until the dogs 65 are engaged by the lugs, resulting in a rotational impact on the anvil 50. As the hammer 25 rebounds and releases the dogs 65, the spring shifts the sleeve 85 and dogs 65 rearwardly causing the other side of the cam surface 108 to force the ball 100 circumferentially within the slot 99. With the dogs 65 retracted from the rotational path of the lug 35, the hammer is reaccelerated for approximately of rotation at which time the ball 100 again engages the surface 108 of the cam 105. Thus an impact on the anvil 50 is produced for each revolution of the rotor shaft 16.

From the drawings and the above description, it can be seen that an impact tool constructed in accordance with the invention provides several desirable features and advantages. For example, by mounting the dogs 65 within the corresponding slots 62 formed within the external surface of the anvil 50 and for axially sliding engagement with the lugs 35 projecting inwardly from the hammer 25, both the hammer 25 and anvil 50 can be economically machined. That is, the cylindrical surfaces 30 and 34 can be easily bored within the hammer 25 so the hammer can include the integral end portion 27 which mounts directly on the rotor shaft 16. This direct mounting is desirable to provide maximum rigidity with minimum play and corresponding wear. Furthermore, the lugs 35 can be conveniently formed by machining the cavities 38 with an end mill. Also, the slot 62 can be easily formed within the external surface of the anvil 50 with standard milling equipment.

The outer cylindrical surface of the hammer 25 provides the hammer with substantial mass outwardly from the axis of rotation of the hammer and this mass provides the hammer with the maximum moment of inertia within a given overall diameter for producing impacts of maximum torque.

The configuration of the anvil 50 also provides an important feature. That is, by forming the axially extending slots 62 within the cylindrical surface 60 on the anvil, maximum torsional rigidity is provided in the anvil to minimize spring back of the hammer 25 and thereby provide positive impact rotation of the driving end portion 52 of the anvil. As can be seen from FIG. 4, by locating the dogs 65 within the grooves 62 formed within the anvil 50 and impacting the dogs with the lugs 35 having conforming curved surfaces 36, the lugs 35 are subjected primarily to radial compression rather than tangential shearing forces which effectively eliminates the changes of shearing the dogs 65. Furthermore, by employing inwardly projecting lugs 35 on the hammer 25, the cavities 38 can each extend through a substantial are for obtaining maximum reacceleration of the hammer 25 after each impact without danger of shearing the lugs 35 from the hammer. The entire mechanism operates in the same manner in a reverse direction of rotation, thus being capable of use in either driving or loosening operations, and with right-hand or left-hand threads.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. In a rotary impact tool including a housing supporting a rotary motor having a shaft, an improved impact mechanism comprising a generally cup-shaped hammer disposed within said housing, means for connecting said hammer to said shaft for rotation therewith, an anvil rotatably supported by said housing and having an outer drive end portion and an inner end portion projecting into said hammer, a spindle extended axially from said inner end portion of said anvil and rotatable therewith, a sleeve mounted on said spindle, spline means connecting said sleeve to said spindle to provide axial movement of said sleeve relative to said anvil and positive rotation of said sleeve with said anvil, means defining a set of axially extending grooves within said anvil, a dog slidably mounted within each said groove for axial movement, means connecting said dogs to said sleeve for axial movement therewith, a corresponding set of lugs projecting inwardly from said hammer, and cam means connecting said hammer to said sleeve for shifting said dogs axially into the path of the corresponding said lugs in response to rotation of said hammer relative to said anvil causing said hammer to produce an impact on said anvil through said dogs.

2. An impact tool as defined in claim 1 wherein said hammer has a cylindrical external surface, said lugs comprising a pair of diametrically opposed lugs projecting inwardly from the forward end portion of said hammer, said anvil having a generally cylindrical outer surface on said inner end portion, and a pair of diametrically spaced and semicylindrical said grooves within said outer surface of said anvil for receiving corresponding said dogs.

3. An impact tool as defined in claim 1 wherein said means for connecting said hammer to said shaft includes an integral end wall on said hammer, and means defining a bore within said end wall for receiving said shaft.

4. An impact tool as defined in claim 1 wherein said inner end portion of said anvil includes means defining a cylindrical bore, said spindle having a head mounted within said bore, and a compression spring mounted on said spindle and extending between said head and said sleeve for urging said sleeve rearwardly within said hammer thereby normally urging said dogs from the rotational path of said lugs.

5. An impact tool as defined in claim 1 wherein said inner end portion of said anvil includes means defining a cylindrical bore for receiving said sleeve, and means defining a corresponding set of radially extending slots within said inner end portion of said anvil for receiving said means connecting said dogs to said sleeve.

6. In a rotary impact tool including a housing supporting a rotatably drive shaft, an improved impact mechanism comprising a generally cup-shaped hammer rotatably mounted in said housing and connected to be driven from said drive shaft, an anvil rotatably supported in said housing and having an outer drive end portion extending from the housing and an inner end portion extending into said cup-shaped hammer, lug means on the interior of said hammer extending radially inward toward but spaced from said anvil, means defining at least one elongated groove extending axially on said inner end portion of said anvil and across the path of rotation of said lug means, a dog slidably mounted in said groove between positions intercepting the path of said lug means and clear of said lug means, a yoke member connected to move said dog between said positions, overload clutch means connecting said anvil and said hammer for simultaneous rotation until rotation of said anvil reaches a predetermined torque, means urging said yoke member toward the position at which said dog clears the path of said lug means, and a connection between said clutch means and said yoke member acting to move said yoke member and said dog toward said lug means in response to disengagement of said clutch means due to resistance to rotation of said anvil.

References Cited UNITED STATES PATENTS 2,825,436 3/1958 Amtssberg 17393.6 2,836,272 5/1958 Kaman 17393.6 3,001,428 9/1961 Sindelar 173-93.6 3,053,360 9/1962 Madsen 17393.6 3,070,201 12/1962 Spyridakis 17393.6 3,174,597 3/1965 Schaedler et al. 17393.6 3,237,703 3/1966 Ramstrom l7393.6

DAVID H. BROWN, Primary Examiner. 

